From the Norman French form of the Welsh name Gwenhwyfar, composed of the elementsgwen meaning "fair, white" and hwyfar meaning "smooth". In Arthurian legend she was the beautiful wife of King Arthur. According to the 12th-century chronicler Geoffrey of Monmouth, she was seduced by Mordred before the battle of Camlann, which led to the deaths of both Mordred and Arthur. According to the 12th-century French poet Chrétien de Troyes, she engaged in an adulterous affair with Sir Lancelot.

The Cornish form of this name, Jennifer, has become popular in the English-speaking world.